Tuck Jumps

click on the image to view a video of this exercise.

Feet hip width or slightly further apart. Feet
pointing forwards or just slightly turned out. Keeping back flat
and head facing forward, bend knees until upper and lower legs are
at 90 degrees. Ensure knees travel in line with feet and heels
remain flat to the floor throughout. Avoid locking the knees when
legs are straight.